wimvb

It seems from the light frame, that the offset is already low. However, several people reported the same problem, with the same camera model. To me, that suggests a camera issue, rather than a flats issue. The uncalibrated light frame has the same colour blotch. It is also very weak, and needs to be stretched a lot to reveal any signal.

The suggested solution is to lower the camera offset. Have you tried that?

Cool! Always nice to see physics in action. Unfortunately that other variable is just outside your fov.

It has been raining so much lately, that my property IS slowly turning into beach front. A few days ago, I spotted swans in this lake-to-be. When it starts freezing, this will be a great place for kids to go ice skating.

Nowadays only clouds are active, it seems. Nice pic.

I think you can safely lower the exposure to one minute, or iso to 400. There is basically no information to the left side of the histogram, so you are losing dynamic range. Otoh, if you overexpose the stars, you will end up with star cores that are difficult to repair. Try to find the exposure time that works best for you. Neve mind what others are using. Your gear + imaging conditions are unique for you. That's why it's important to experiment to find the best settings.

That's a very nice Pleiades, especially for the very short integration time. You will need more data to bring the noise down.

Yes, but a guidescope in those rings, on a finder shoe on a scope mounted in guider rings. That looks like a recipe for differential flexure, imo.

No walking noise. In fact, almost no drift at all between exposures. Very accurate tracking.

Yeah, but I must have thought that no needle can be fast enough to keep up with video signals. 😁

Are imaging nights getting shorter already? Oh my, I haven't even started yet.

I wonder how many patents we have between us. Mine are only illusionary.

Some careful stretching later:

No one ever said that astrophotography is easy. Welcome to the club of problem solvers. (Or as they say in the software business: "there's always one more bug.") 😋

Those zip files are rather large. Lights.zip now at 1.3 GB and loading ...

NICE! I've heard that Microsoft ICE does a good job. Also PixInsight has several tools for making mosaics.

Isn't that a zoom lens? 😉

Besides the already mentioned focus issues, you might also revise your calibration and stacking process. Your masters still have a lot of hot pixels. Plus there are a number of dust bunnies that can be removed by using flats.

Great report, Göran. And I'm not jealous at all. 😉 For as Orup put it : "Jag har bara regn hos mig". Have fun down under.

Great start in AP. What does "BPM" stand for?

Interesting. I would like to see the transmission curves for these filters. IDAS are generally good quality LP filters, but if the zwo cover glass isn't as good, what are the chances of the combination causing unwanted reflections?

When I was a kid, I got the idea to hook up a simple audio tape recorder to a tv, to record programs, but I didn't have the means. Only a few years later did I see a vhs recorder.

Great start. You seem to have focus and tracking under control. Once you have good data, you can process it as many times as you want, and improve as you learn. I agree with @vlaiv that you should try to avoid clipping the background, but I wouldn't go so far as not having one single pixel clipped in the final image. Avoid clipping while you process. Then at the very end of processing, bring the general background level down with a curves stretch, using an S-curve, until you get a pleasing image. Your image seems predominantly red. Early on in your process, look for an "empty" background area and line up the histograms for red, green and blue. You can compare your image to an image you found online to determine a suitable area. One of the reasons you image looks red is that most of your noise seems in the red channel. There is really only one good method for noise reduction: get more data. If you have light pollution, you have to compensate for that by increasing the total integration time. As for the core of M42. It is very tricky to keep that under control while lifting the outer regions. What does your unstretced image look like? Are the 4 stars that make up the trapezium in the core of the nebula visible? If so, then it is possible to stretch the image to show both the core and the fainter areas. But it's going to be difficult. And I have no idea how to do that with GIMP. If the core is blown out, there's no way to rescue it, other than with new data. Have a look here: That image used 50 20 second subs.

Yes, that should be fun. Good luck.

Just getting better and better. The outer regions of this galaxy are very thin, and using red as luminance won't help bring it out, unfortunately. Hopefully you can collect "real" luminance soon.